A brief study of bridges
We build different bridges for different needs
Covered Bridge
Covered Bridges
In the 18th and 19th century many bridges were covered
Covered Bridges
Why do you think these bridges were covered?
Covered Bridges
Some say it was for protection from a sudden storm
Covered Bridges
Some say to keep horses from shying at the sight of rippling water
Covered Bridges
Some say to provided a romantic setting for a hug or kiss
Covered Bridges
However…
Covered Bridges
The real reason was to protect the timber from the effects of rain and snow 
Beam Bridge
Beam Bridge
The simplest and least expensive
Beam Sometimes called a girder
Beam Bridge
Can be made of steel
Beam Bridge
Concrete
Beam Bridge
or even wood
Beam Bridge
Not the best for long or high spans
Suspension Bridge
Suspension Bridge
Better for Long spans
More Majestic
First suspension bridge in America Newburyport, Mass.
Built around 1900
Golden Gate Bridge
Perhaps the most famous bridge in the world
Why is it called the Golden Gate?
Golden Gate Bridge
Perhaps the most famous bridge in the world
It spans the Golden Gate Strait
The worlds 10 longest spans are all suspension bridges
Arch Bridge
Arch Bridge
Very strong
Can last a very long time
Arch Bridge
This is Pont du Gard a 2000 year old Roman aqueduct
Arch bridge
This is a bridge built so that a stream of water could cross a stream of water
Cable Stayed Bridge
Cable Stayed bridge
Elegant structure
Long spans
Sunshine Skyway Bridge
St. Petersburg, FL
Requires less material
Requires Less labor
Sunshine Skyway Bridge
St. Petersburg, FL
Similar to Clark bridge in Alton, IL
Lift Bridge
Lifting Bridge
Do you know the name of this bridge?
Lifting Bridge
It is not London Bridge.
Lifting Bridge
It is over 100 years old
Tower Bridge
Truss Bridge
Truss Bridge
A truss can support from above
Truss Bridge
A truss can also support from below
Truss Bridge
What do you know about this bridge?
Eads Bridge
St. Louis, MO
Completed in 1874
American masterpiece
A quick review
Covered Bridges
Makes use of local building supplies
Covered Bridges
Interior truss makes it stronger than wood beam bridge
Covered Bridges
Covering the timbers makes them last longer
Beam Bridge
Easiest to build
Least expensive design
Cable Stay Bridge
Less expensive to build than suspension bridges
Cable Stay Bridges
Uses less material than suspension bridge
Cable Stay Bridges
They look cool!
Cable Stay Bridges
Requires the use of more modern materials
Suspension Bridges
Longest unsupported spans
Suspension Bridges
They look pretty cool too!
Arched Bridges
Strong
Durable
Ancient/low tech building materials
Labor intensive
Truss Bridge
Stronger than beam bridge
Think Vectors!
Truss Bridge
Can bridge longer unsupported spans than a beam bridge
Lifting Bridge
Blocks trafic
Lifting Bridge
Allows the passage of ships
Lifting Bridge
Rather expensive
Subject to mechanical breakdown
Many different bridges for many different jobs
See these websites for more information on bridge design
http://www.howstuffworks.com/bridge.htm

http://www.pbs.org/wgbh/nova/bridge/

http://myron.sjsu.edu/romeweb/engineer/art2.htm

http://www.bardaglea.org.uk/bridges/welcome.html

http://education.sdsc.edu/enrich/downloadables/bridges.pdf

http://www.tfhrc.gov/pubrds/summer95/p95su23.htm